In line with advancement of wireless communications in terms of increased speed and capacity and advancement of wireless devices in terms of reduced size, there is an increasing demand for an antenna that operates in a millimeter wave band (not lower than 30 GHz and not higher than 300 GHz). Since a higher frequency causes a greater conductor loss and a greater dielectric loss, it is important that an antenna that operates in a millimeter wave band be designed so that a conductor loss and a dielectric loss are reduced.
As a transmission line for transmitting an electromagnetic wave in a millimeter wave band, a waveguide is suitably used. As an antenna for radiating an electromagnetic wave in a millimeter wave band, a comb-line microstrip antenna is suitably used.
Patent Literature 1 discloses a comb-line microstrip antenna. Patent Literature 2 discloses an antenna in which a waveguide is attached to a comb-line microstrip antenna.